About Guided Wave Radar

Rosemount™ guided wave radars are easy to install and virtually unaffected by process conditions.


Reduce Maintenance, Increase Safety and Optimize Your Process

We have developed products using advanced radar technology since 1974, and our continuous improvement approach has resulted in radar transmitters that provide superior performance and reliability.

Guided wave radar devices have no moving parts and require minimum maintenance. They can measure both level and the interface between two media.

The technology is not affected by media density, varying temperatures or pressures, and provides reliable, accurate measurements in demanding applications. 

How It Works

Guided wave radar is based on microwave technology. Microwaves are only affected by materials that reflect energy which means that temperature variations, dust, pressure and viscosity do not affect accuracy.

The device sends a low energy microwave pulse down a probe. When the pulse hits the media, a significant proportion of the energy is reflected back up the probe to the device. The level directly proportional to the time domain reflectometry. Because a proportion of the emitted pulse will continue down the probe, an interface can also be detected.


In most processes varying conditions are common. Temperature, density and viscosity may change. Variations in level measurement can easily occur under these conditions, but the guided wave radar technology is unaffected by these changes. The device does not need to compensate for changes in density, dielectric or conductivity in the fluid and this makes this top down measurement very robust.


With just one device you can measure both level and interface.

In separation processes, it is often necessary to measure both the level and the interface level. One example is oil on water. When microwaves hit the oil surface some are reflected back and some continue through the oil. The reflected microwaves provide the level reading and the microwaves that continue through the oil will be reflected back on the water surface. These microwaves then provide the interface reading.


Level measurement using guided wave radar technology is based on the reflection of microwaves on surface media.

All media have a dielectric constant. The higher it is, the stronger the reflection of the microwaves will be. Vacuum gives no reflection at all and has a dielectric constant of 1. Oil is approximately 2 and water around 80.

A dielectric constant below 1.5 is often challenging to measure, but the high sensitivity guided wave radar level transmitters from Emerson handle it with ease.


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